The present invention relates to apparatus and methods for discriminating between an EGR temperature sensor fault and operating conditions which may produce a similar sensor signal.
As engine technology becomes increasingly more sophisticated, the number and variety of sensors used in controlling the engine has continued to climb. Typical engines may include 20 or more sensors used to provide information to the vehicle owner, operator, and service personnel and/or used to control the engine. Sensors may be used to provide engine protection by quickly detecting adverse operating conditions which may indicate a fault or malfunction to reduce or eliminate any permanent engine damage. The engine control module (ECM) monitors the sensor inputs to detect conditions which may trigger a diagnostic code or fault which may be used by owners/operators and/or service and maintenance personnel to troubleshoot and repair the engine.
In addition to monitoring sensor inputs to detect potential engine problems, the ECM typically includes logic to detect whether the sensor itself is functioning properly. However, depending upon the particular sensor, it is often difficult to determine whether the sensor is malfunctioning or whether the sensor is accurately detecting an actual engine condition. Setting an inappropriate diagnostic code may lead to unnecessary replacement of sensors or other components with the attendant increase of maintenance and warranty costs. As such, it is desirable to provide control logic which can detect a faulty sensor and set an appropriate fault or diagnostic code by discriminating between signals which indicate an actual engine condition and similar or identical signals which indicate a sensor fault.
An object of the present invention is to provide a system and method for accurately detecting a sensor fault.
Another object of the present invention is to provide a system and method for detecting a high-voltage fault for an EGR temperature sensor.
A further object of the present invention to improve the reliability of fault codes set by the ECM.
Yet another object of the present invention is to provide a sensor fault detector which uses secondary indicators to determine the reliability of the sensor signal.
Another object of the present invention is to provide an engine control system and method which detects a failed EGR temperature sensor based on signals received from at least one other engine or vehicle sensor.
A further object of the present invention is to provide a system and method for accurately detecting a sensor malfunction by suppressing a corresponding fault code for a period of time after engine start.
In carrying out the above objects, and other objects, features, and advantages of the invention a system and method for detecting a failed EGR temperature sensor include monitoring the sensor signal and comparing the signal to a threshold. When the signal or corresponding value crosses the associated threshold, secondary indicators are examined to discriminate between a failed sensor and an accurate sensor signal. In one embodiment, the secondary indicators include at least one other temperature sensor, such as an ambient air temperature sensor, a coolant temperature sensor, and/or an oil temperature sensor which may be used to infer a likely temperature or temperature range for the sensor in question. In another embodiment of the present invention, the secondary indicator is an elapsed time after engine start which may also be used to infer a likely temperature or temperature range for the sensor being monitored. In this embodiment, a sensor fault code is suppressed for a calibratible period of time after an engine start.
The present invention provides a number of advantages. For example, the present invention reduces false diagnostic or fault codes which may lead to unnecessary sensor or component replacement. The invention also allows detection of a sensor failure based on a signal which is similar or identical to a properly functioning sensor using secondary indicators, such as other sensors, or elapsed engine running time. As such, the present invention provides inherent redundancy without requiring a redundant sensor.
The above advantages, and other advantages, objects, and features of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.